Steviol glycoside solutions

ABSTRACT

Steviol glycoside solutions, and methods of making steviol glycoside solutions, are described. The steviol glycoside solutions are clear and stable, and have clear solution stability, for extended periods of time.

BACKGROUND OF THE INVENTION

The invention is directed to a process for producing a stable steviolglycoside solution which can be used as a sweetener, flavor, flavorenhancer, and the like, in food, beverage and other products.

Sugar alternatives are receiving increasing attention due to awarenessof many diseases in conjunction with consumption of high-sugar foods andbeverages. However, many artificial sweeteners such as dulcin, sodiumcyclamate and saccharin were banned or restricted in some countries dueto concerns on their safety. Therefore non-caloric sweeteners of naturalorigin are becoming increasingly popular. The sweet herb Steviarebaudiana produces a number of diterpene glycosides which feature highintensity sweetness and sensory properties superior to those of manyother high potency sweeteners.

The above-mentioned sweet glycosides, have a common aglycon, steviol,and differ by the number and type of carbohydrate residues at the C13and C19 positions. The leaves of Stevia are able to accumulate up to10-20% (on dry weight basis) steviol glycosides. The major glycosidesfound in Stevia leaves are rebaudioside A (2-10%), stevioside (2-10%),and rebaudioside C (1-2%). Other glycosides such as rebaudioside B, D,E, and F, steviolbioside and rubusoside are found at much lower levels(approx. 0-0.2%).

Two major glycosides—stevioside and rebaudioside A (reb A), have beenextensively studied and characterized in terms of their suitability ascommercial high intensity sweeteners. Stability studies in carbonatedbeverages confirmed their heat and pH stability (Chang S. S., Cook, J.M. (1983) Stability studies of stevioside and rebaudioside A incarbonated beverages. J. Agric. Food Chem. 31: 409-412.)

Steviol glycosides differ from each other not only by molecularstructure, but also by their taste properties. Usually stevioside isfound to be 110-270 times sweeter than sucrose, rebaudioside A between150 and 320 times, and rebaudioside C between 40-60 times sweeter thansucrose. Dulcoside A is 30 times sweeter than sucrose. Rebaudioside Ahas the least astringent, the least bitter, and the least persistentaftertaste thus possessing the most favorable sensory attributes inmajor steviol glycosides (Tanaka O. (1987) Improvement of taste ofnatural sweeteners. Pure Appl. Chem. 69:675-683; Phillips K. C. (1989)Stevia: steps in developing a new sweetener. In: Grenby T. H. ed.Developments in sweeteners, vol. 3. Elsevier Applied Science, London.1-43.)

Methods for the extraction and purification of sweet glycosides from theStevia rebaudiana plant using water or organic solvents are describedin, for example, U.S. Pat. Nos. 4,361,697; 4,082,858; 4,892,938;5,972,120; 5,962,678; 7,838,044 and 7,862,845, each of which isincorporated by reference herein in its entirety.

In addition to extracted and purified sweet glycosides, modified steviolglycosides are often used due to the enhanced functional andorganoleptic properties achieved by the modification.

Despite the benefits of using steviol glycosides and their modifiedforms, solubility and clear solution stability of steviol glycosidesremain as issues with using steviol glycosides in consumer food andbeverage products, particularly in those products that are made on acommercial scale. Stevia-derived ingredients, particularly those withhigher purity levels, face solubility challenges in aqueous solutions.While crude Stevia leaf extracts may be water soluble, when the steviolglycosides from the leaf extract are purified, the steviol glycosidesbecome difficult to solubilize and maintain in solution. Purifiedsteviol glycoside extracts have water solubility values that typicallyrange from 0.05% to 1% (w/w) at room temperature, and are difficult tomaintain in clear solution form for extended periods of time.

Commercial food and beverage production typically requires the use ofstable ingredients that are able to be delivered in various forms whichare able to withstand variations in temperature, force, chemicalinteractions with other ingredients, and the like.

There is a need, therefore, to provide a steviol glycoside solution thatcan be used in liquid form and remain stable over time and under variousconditions.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming the issues with usingsteviol glycosides in liquid form. The invention describes a process forproducing a stable, clear liquid steviol glycoside ingredient that canbe used in various food products and beverages as a sweetener, asweetness enhancer, a flavor, and/or a flavor modifier.

The process of the invention includes the steps of providing a steviolglycoside, combining it with a polyol, such as propylene glycol,optionally heating the combination with agitation, and then cooling thecombination to result in the liquid steviol glycoside ingredient. Theliquid steviol glycoside ingredient is a clear solution that is stablefor an extended period of time under varying conditions. In certainembodiments, the liquid steviol glycoside ingredient is a visibly clearsolution that is stable for at least 45 days.

The liquid steviol glycoside ingredient comprises steviol glycosidesfound in the Stevia rebaudiana plant. The steviol glycosides areselected from the group that includes stevioside, any rebaudioside suchas rebaudioside A, rebaudioside B, rebaudioside C, rebaudioside D,rebaudioside E, rebaudioside F, rebaudioside I, rebaudioside M,rebaudioside N, rebaudioside O, dulcoside A, steviolbioside, rubusoside,as well as other steviol glycosides found in the Stevia rebaudianaplant, and mixtures thereof. In one embodiment, the steviol glycosidesare highly purified steviol glycosides having a purity of greater than,for example, 90%, 95%, 97% or 99%. Non-limiting examples of highlypurified steviol glycosides include highly purified rebaudioside A andhighly purified rebaudioside D. Processes for purifying steviolglycosides is described in U.S. Pat. Nos. 7,862,845, 8,293,302, and8,377,927, each of which is incorporated by reference herein in itsentirety.

In other embodiments, the steviol glycosides may be used in the form ofa Stevia extract comprising a mixture of steviol glycosides. The extractmay be taken from any step of the aqueous extraction process, forexample, as described in U.S. Pat. No. 7,838,044. The extract maycontain a near-native ratio of steviol glycosides as found in the plant,or may be subjected to intermediate extraction and/or purification stepsto provide a desired concentration and ratio of steviol glycosides. Incertain embodiments, desired concentrations of certain steviolglycosides, such as rebaudioside A, rebaudioside B, rebaudioside D, etc.are present in the Stevia extract.

The liquid steviol glycoside ingredient may additionally oralternatively comprise modified steviol glycosides, such as glucosylatedsteviol glycosides. Glucosylated steviol glycosides have one or moreglucose units attached to the C-13 and/or the C-19 position of thesteviol glycoside structure. In certain embodiments, 1 to 2 glucoseunits are added. In other embodiments, 3 to 9, or 10 to 20, or somecombination thereof, of glucose units are added to the steviolglycosides. Some methods for glycosylating steviol glycosides aredescribed in U.S. Pat. Nos. 8,257,948, 8,318,232, 8,318,459, 8,323,716,8,501,261, 8,669,077, 8,735,101, 8,911,971, 8,993,269 and 9,055,761,each of which is incorporated by reference herein it its entirety.Glucosylated steviol glycosides have been found to impact the sweetnessand/or the flavor profile of the products to which they are added.

In one embodiment, the steviol glycoside is first subjected to agradient heating process to enhance its solubility. The solubility ofthe steviol glycoside can be also enhanced by using a gradient coolingprocess after the gradient heating process. Examples of such gradientheating and gradient cooling processes are described in U.S. Pat. No.8,993,028, and US Patent Application Publication No. 20130330463, eachof which is incorporated by reference herein in its entirety.

The obtained liquid steviol glycoside ingredient may be applied invarious foods and beverages as sweeteners, sweetness enhancers, flavorenhancers, and flavor modifiers, including soft drinks, liquid beverageenhancers, non-carbonated beverages, ice cream, cookies, bread, fruitjuices, milk or dairy products, baked goods and confectionary products.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION OF THE INVENTION

Advantages of the present invention will become more apparent from thedetailed description given hereinafter. However, it should be understoodthat the detailed description and specific examples, while indicatingpreferred embodiments of the invention, are given by way of illustrationonly, since various changes and modifications within the spirit andscope of the invention will become apparent to those skilled in the artfrom this detailed description.

The solubility and clear solution stability of steviol glycosideingredients has impacted their use in systems in which eithersolubility, or clear solution stability, or both, are important factors.Typical steviol glycoside ingredients have water solubility levelsranging from less than 0.01% to about 2% at room temperature. Even if asteviol glycoside ingredient has a suitable solubility, the stability ofthe resulting solution is often for a short period of time, oftenranging from a few minutes to a few hours, making it difficult to usesuch solutions in commercial production processes.

As used herein, the term “solubility” shall be defined as the ability ofa steviol glycoside to form a visibly clear solution. The expression“clear solution stability” shall be defined as the time period overwhich the steviol glycoside solution remains clear. “Clear” as usedherein shall be defined as visibly clear, and free of visibleprecipitation or turbidity. The use of the expression “steviolglycosides” shall include any steviol glycoside, combinations of steviolglycosides, and modified forms of steviol glycosides.

Steviol glycoside ingredients can be used in highly purified forms, orin blends that provide functional and organoleptic advantages. Blendsmay include two or more steviol glycosides or modified steviolglycosides, in various ratios depending on the desired result. In someblends, one steviol glycoside may form the majority of the blend, or thesteviol glycosides may be present in approximately equal amounts in theblend. Other forms of steviol glycoside ingredients include extracts,which may be minimally processed to remove most of the plant impurities,or moderately or highly processed to increase the concentration ofdesired steviol glycosides in the extract.

In one embodiment, it was surprisingly discovered that using propyleneglycol, or other polyols, to solubilize steviol glycoside ingredients,and particularly steviol glycoside blends, provides solubility and clearsolution stability to the resulting solution. The propylene glycol isprovided in an aqueous solution in a concentration ranging from about10-50% w/w (propylene glycol to water.) The steviol glycoside, whether apurified form or a blend, is added to the propylene glycol, which isoptionally first heated to a temperature of between about 70° C. toabout 90° C., or about 75° C. to about 85° C. In certain embodiments,the propylene glycol is first heated to a temperature of about 80° C.Upon adding the steviol glycoside ingredient to the propylene glycol orthe heated propylene glycol, the mixture is agitated continuously untilthe steviol glycoside is completely dissolved. The resulting solution isvisibly clear, and has a clarity that is similar, substantiallyequivalent, or equivalent to the clarity of pure water.

In another embodiment, it was surprisingly discovered that propyleneglycol in an essentially water-free system is able to solubilize steviolglycoside ingredients, particularly steviol glycoside extracts, andresults in a highly concentrated steviol glycoside ingredient solution,and provides superior solubility and clear solution stability to theresulting solution. As used herein, the expression “essentiallywater-free system” means that no quantifiable amount of water is addedto the system, and any water present in the system is merely a traceamount that may be inherently contained in the components of thesolution.

If the propylene glycol or other polyol was heated, the liquid steviolglycoside ingredient solution is then cooled to room temperature ofabout 20° C. to 25° C. for further use. The resulting solution remainsclear for an extended period of time, ranging from 1 week to over 1month.

It was unexpectedly discovered that relatively high concentrationsteviol glycoside ingredient solutions can be prepared with this method,with concentrations ranging from about 5% to 40% by weight, as comparedto conventional solubility levels as described above. This represents anapproximately 2.5 to 4000 times increase in solubility as compared toaqueous solutions of the same steviol glycoside ingredient. In someembodiments, a solubility increase of 2000 times the aqueous solubilityof the same steviol glycoside ingredient was observed. Even at thesehigh concentrations, the steviol glycoside ingredient solutions remainedclear over time.

The following Examples are intended to enable and exemplify, and notlimit, the invention, the full scope of which is defined in the appendedclaims.

COMPARATIVE EXAMPLE 1 Tabletop Steviol Glycoside Sweetener

A commercially available tabletop steviol glycoside sweetener wasevaluated for its solubility in water and in propylene glycol, based onthe instructions provided at (website.)

3 g of the tabletop sweetener was mixed with 9 ml of propylene glycol,resulting in a 30% mixture. The mixture was microwaved, shaken by hand,and cooled, and the process repeated 6 times. The mixture formed ahighly viscous, gritty, opaque paste.

COMPARATIVE EXAMPLE 2 Commercially Available Highly Purified SteviaIngredient

Reb A 97, available from Tereos PureCircle Solutions(www.stevia-tereos-purecircle.com), was combined with propylene glycolin the same manner as Comparative Example 1. A similar viscous, gritty,opaque paste was formed.

EXAMPLE 1 Blend of Steviol Glycoside Ingredients

A blend of three commercially available steviol glycoside ingredientswas prepared, as follows:

TABLE 1A Steviol Glycoside Ingredient Amount (% w/w) Reb A + Stevioside≥75 Reb C + Stevioside ≥8 Total steviol glycosides ≥95

A series of propylene glycol solutions was prepared, and each one washeated to about 80° C. The steviol glycoside blend was added to thepropylene glycol solution at various concentrations, under constantagitation and while maintaining the temperature of the solution at about80° C. The time to form a clear steviol glycoside solution was measured.The resulting steviol glycoside ingredient solutions were allowed tocool, then each solution was divided into two samples, with one samplebeing held at room temperature (about 20° C.) while the other sample wasstored under refrigeration at a temperature of about 4° C. The clearsolution stability of the steviol glycoside ingredient solution wasmeasured over 60 days. The results are shown in Table 1B.

TABLE 1B % Stevia 5% 10% 20% 25% 30% 40% Blend I  10 g  20 g  40 g  50 g 60 g  80 g Propylene Glycol 100 g 100 g  80 g  75 g  70 g  60 g Water 90 g  80 g  80 g  75 g  70 g  60 g Total 200 g 200 g 200 g 200 g 200 g200 g Stability at Room Clear Clear Clear Clear Slightly SlightlyTemperature for 60 Days cloudy cloudy Stability at Refrigeration ClearClear Clear Clear Slightly Slightly Temperature for 60 Days cloudycloudy

EXAMPLE 2 Solubility of Various Stevia Sweeteners in 50:50 Ratio ofPropylene Glycol and Water

A solution of 50% propylene glycol and 50% water was heated to about 80°C. Each Stevia blend was tested at various concentrations to determinethe maximum solubility of products. The steviol glycoside blend wasadded to the propylene glycol solution at various concentrations, underconstant agitation and while maintaining the temperature of the solutionat about 80° C. The time to form a clear steviol glycoside solution wasmeasured. The resulting steviol glycoside ingredient solutions wereallowed to cool, then each solution was divided into two samples, withone sample being held at room temperature (about 20° C.) while the othersample was stored under refrigeration at a temperature of about 4° C.The clear solution stability of the steviol glycoside ingredientsolution was measured over 60 days. The blend compositions are shown inTable 2A, and the solubility and clarity results are shown in Table 2B.

TABLE 2A Sample Stevia Blend Total Steviol Glycosides (%) 1 RebaudiosideA ≥ 50% ≥95% 2 Rebaudioside A ≥ 97% ≥95% 3 Rebaudioside A ≥ 99% ≥95% 4Rebaudioside B ≥95% 5 Rebaudioside A ≥ 70% ≥95% 6 Rebaudioside D ≥ 50%≥95%

TABLE 2B Sample Comments 1 20% w/w clear and stable over 1 month 2 20%w/w clear and stable over 1 week, solid at 1 month 3 Did not dissolve 420% w/w went solid within 30 minutes 5 20% w/w clear and stable for 1week, semi-solid paste at over 1 month 6 Tried at 10% w/w, formed aninsoluble paste

Liquid Beverage Enhancers

Liquid beverage enhancers, commonly referred to as “drops,” have becomequite popular for flavoring, sweetening, coloring, or enhancingbeverages, such as water, tea, coffee, or other aqueous beverages. Thesebeverage enhancers are typically clear solutions and generally comprisea high concentration of a sweetener dissolved in water. The highconcentration is required in order for just one or a few drops of theenhancer to sweeten, flavor, or otherwise enhance a standard serving ofa beverage, such as 8, 16 or 24 ounces of the beverage.

Consumers expect these enhancers to be clear and free from visiblecrystals or cloudiness during the shelf life of these enhancers. Otherenhancers, such as some coffee enhancers, need not necessarily be clear,but can resemble milk or cream and are desirably smooth and flowable intheir consistency without crystals or granules in the enhancer.

It was unexpectedly discovered that by using an essentially water-freesystem, liquid beverage enhancers using only Stevia-based ingredients asthe sweetener can be prepared, and remain clear and stable over thedesired shelf life of the enhancer. In certain embodiments, theStevia-based ingredients are present in an amount ranging from 5-10%w/w, such as 8% or 9% by weight. In one embodiment, the essentiallywater-free system comprises food-grade propylene glycol. Otherfood-grade polyols include glycerol, sorbitol and mannitol.

EXAMPLE 3 Liquid Beverage Enhancer

A liquid beverage enhancer was made using the formula listed in Table 3.

TABLE 3 Ingredient Amount Propylene Glycol 34.25 ml Stevia Extract    3g Malic Acid   10 g Potassium Sorbate  0.5 g Potassium Citrate  1.25 gFlavor 0.825 g

The liquid beverage enhancer was prepared using the following procedure.A measured volume of propylene glycol was heated and maintained at 80°C., then malic acid was added, sonicated and periodically vortexed todissolve the malic acid in the propylene glycol. The Stevia extractpowder was then added and dissolved, followed by adding the potassiumsorbate which also was dissolved. Potassium citrate was added, sonicatedand periodically vortexed until the potassium citrate was alsodissolved. The solution was then cooled down to room temperature, andthe flavor was added and mixed well to form the liquid beverageenhancer.

The sequence of steps described above may be changed, with some stepsomitted, or otherwise altered, to produce the liquid beverage enhancer.

It is to be understood that the foregoing descriptions and specificembodiments shown herein are merely illustrative of the best mode of theinvention and the principles thereof, and that modifications andadditions may be made by those skilled in the art without departing fromthe spirit of the invention, the full scope of which is defined by theappended claims.

What is claimed is:
 1. A method of making a stable, clear liquid steviolglycoside ingredient solution, comprising the steps of: a. providing asteviol glycoside; b. providing a solvent system comprising 10-100% w/wpropylene glycol; and c. combining the steviol glycoside in the solventwith constant agitation and while maintaining the temperature of thesolvent until the steviol glycoside is dissolved; wherein the stable,clear liquid steviol glycoside ingredient solution has a clear solutionstability at a steviol glycoside concentration of up to 40% w/w for45-60 days.
 2. The method of claim 1, wherein the steviol glycoside ismade by a gradient heating and gradient cooling process.
 3. The methodof claim 1, wherein the propylene glycol is 10-50% w/w.
 4. The method ofclaim 1, wherein the solvent system is heated prior to combining thesteviol glycosides in the solvent.
 5. The method of claim 4, wherein thesolvent system is heated to a temperature of about 70° C. to about 95°C.
 6. The method of claim 1, wherein the steviol glycoside ingredientsolution is cooled after dissolving the steviol glycoside.
 7. The methodof claim 6, wherein the steviol glycoside ingredient solution is cooledto about 20° C.
 8. The method of claim 1, wherein the steviol glycosideingredient solution is visibly clear and free of visible cloudiness orturbidity.
 9. The method of claim 1, wherein the steviol glycoside isselected from one or more of the following: Reb A, Reb B, Reb C, Reb D,Reb E, Reb F, Reb I, Reb M, Reb N, Reb O, Reb Q, Reb R, Dulcoside A,Rubusoside, Stevioside, Steviolbioside, and combinations thereof.